docs: def clust_coef(self, node):
          """
          Computes and returns the local clustering coefficient of node.  The
          local cluster coefficient is proportion of the actual number of edges between
          neighbours of node and the maximum number of edges between those neighbours.
  
          See <http://en.wikipedia.org/wiki/Clustering_coefficient#Local_clustering_coefficient>
          for a formal definition.
          """
          num = 0
          nbr_set = set(self.out_nbrs(node))
  
          if node in nbr_set:
              nbr_set.remove(node) # loop defense
  
          for nbr in nbr_set:
              sec_set = set(self.out_nbrs(nbr))
              if nbr in sec_set:
                  sec_set.remove(nbr) # loop defense
              num += len(nbr_set & sec_set)
  
          nbr_num = len(nbr_set)
          if nbr_num:
              clust_coef = float(num) / (nbr_num * (nbr_num - 1))
          else:
              clust_coef = 0.0
          return clust_coef